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Thread: Passive Heatsinking Only - Comments

  1. #41
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    No I suggested another IC a bit higher in this page that has simple on/off temp control
    He wants proportional control, which I think to be overkill that's all

  2. #42
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    I didn't see this thread, must have been done during my absence, but two things that I didn't see when I scanned it quickly jusrt now:
    Centrifugal fans can be better, higher torque and lower speed air flow, so more quiet for a given cooling capacity and more able to fit in low profile cases. The other thing (that might be said before) is to use a thick base plate. As well as more optical stability, you can couple everythign that gets hot right to that plate, then just cool the plate, and do it on a surface where dust isn't going to harm anything. You can stick dividers and partitions around the 'floor' to screen from dust, and the whole projector gets 'central cooling'. Also, that limits the temperature rise of the whole system, so everything is more reliable, and you don't need much airflow, just GOOD airflow, it has to slowly and gently displace all the hot air that otherwise collects against the surface. That's all it has to do because if the temperature rise is small and slow, the airflow that removes the heat can also be small and slow, it just has to be consistent and unrestricted.

    For boards that have heatsinks of their own and no easy way to clamp them to the base plate directly, consider bending a cheap commercial CPU heatpipe based sink into place to carry heat silently from board to plate.

    If the projector can be mounted vertically and has a big vaned panel like MechEng3 showed, it might not need a fan. I've seen DPSS lasers with fans that might as well be absent, once you fit the head to a heatsinking baseplate. Same logic can be extended where possible to the entire system.

    For fan speed reduction, a smal metal film resistor in series can work well. For proportional control, an LM317 regulator might be enough, especially in current control mode with a linear controller based round a pot and a 1.25V reference. Might be able to add a thermistor to the sense network for automated control too.

  3. #43
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    Quote Originally Posted by FourDee View Post
    No I suggested another IC a bit higher in this page that has simple on/off temp control
    He wants proportional control, which I think to be overkill that's all
    You're right, I could do. But as picky as it sounds, I only want the fans to run full blast if they have to. (Dust/Noise/Thermal balance etc. etc.) I'm hoping the fans will remain off for a good proportion of the time, but should the temperature inside the case rise (due to whatever the conditions outside are) then the facility is there to autonomously kick them in, should the scanner want to cool down.
    Sort of a set and forget thing...
    I'm hoping that this temp. control would in fact make it better for a 473 DPSS's stability, not worse.

    Ta,
    Dan

  4. #44
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    Quote Originally Posted by danielbriggs View Post
    You're right, I could do. But as picky as it sounds, I only want the fans to run full blast if they have to. (Dust/Noise/Thermal balance etc. etc.) I'm hoping the fans will remain off for a good proportion of the time, but should the temperature inside the case rise (due to whatever the conditions outside are) then the facility is there to autonomously kick them in, should the scanner want to cool down.
    Sort of a set and forget thing...
    I'm hoping that this temp. control would in fact make it better for a 473 DPSS's stability, not worse.

    Ta,
    Dan
    Glad you brought this up Dan. The whole intention of me starting this thread was my hatred of fan noise. If I can't get truly passive cooling you're suggestion is the next best thing. I can't see the point in having fans running all the time if they are not necessary.

    I've noticed that when I run my projector even for quite a few hours it barely gets warm, in this case it is pointless having fans running, particularly as my blue prefers to be a bit warm to get a really nice stable beam output.

    O.K., so at a gig the fan noise doesn't matter as it's drowned out by the music or whatever. BUT... when i'm running the projector at home for my own entertainment I hate the noise of fans with a passion.

    Cheers

    Jem
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

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